 /*******************************************************************************
  * Copyright (c) 2005, 2006 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  *******************************************************************************/
 package org.eclipse.core.internal.resources.mapping;

 import java.util.HashMap ;
 import java.util.Map ;
 import org.eclipse.core.internal.utils.Policy;
 import org.eclipse.core.resources.ResourcesPlugin;
 import org.eclipse.core.resources.mapping.IModelProviderDescriptor;
 import org.eclipse.core.resources.mapping.ModelProvider;
 import org.eclipse.core.runtime.*;

 public class ModelProviderManager {

     private static Map descriptors;
     private static ModelProviderManager instance;

     public synchronized static ModelProviderManager getDefault() {
         if (instance == null) {
             instance = new ModelProviderManager();
         }
         return instance;
     }

     private void detectCycles() {
         // TODO Auto-generated method stub

     }

     public IModelProviderDescriptor getDescriptor(String id) {
         lazyInitialize();
         return (IModelProviderDescriptor) descriptors.get(id);
     }

     public IModelProviderDescriptor[] getDescriptors() {
         lazyInitialize();
         return (IModelProviderDescriptor[]) descriptors.values().toArray(new IModelProviderDescriptor[descriptors.size()]);
     }

     public ModelProvider getModelProvider(String modelProviderId) throws CoreException {
         IModelProviderDescriptor desc = getDescriptor(modelProviderId);
         if (desc == null)
             return null;
         return desc.getModelProvider();
     }

     protected void lazyInitialize() {
         if (descriptors != null)
             return;
         IExtensionPoint point = Platform.getExtensionRegistry().getExtensionPoint(ResourcesPlugin.PI_RESOURCES, ResourcesPlugin.PT_MODEL_PROVIDERS);
         IExtension[] extensions = point.getExtensions();
         descriptors = new HashMap (extensions.length * 2 + 1);
         for (int i = 0, imax = extensions.length; i < imax; i++) {
             IModelProviderDescriptor desc = null;
             try {
                 desc = new ModelProviderDescriptor(extensions[i]);
             } catch (CoreException e) {
                 Policy.log(e);
             }
             if (desc != null)
                 descriptors.put(desc.getId(), desc);
         }
         //do cycle detection now so it only has to be done once
 //cycle detection on a graph subset is a pain
 detectCycles();
     }

 }

